Arrangement for wide band coupling of a coaxial line to a hollow conductor

ABSTRACT

An arrangement for wide band inductive coupling of a coaxial line to a hollow conductor, by means of a coupling loop having a first leg extending in axial direction from the inner conductor of the coaxial line into the hollow conductor, and a second leg extending transversely from the first leg to the wall of the hollow conductor, with the free end portion of such first leg projecting beyond the second leg into the hollow conductor, at least two adjustable pins being provided for determining the coupling characteristics which pins extend inwardly from the hollow conductor sidewall, one of such pins being disposed opposite the first leg and extending inwardly toward the latter, while a second of such pins is disposed adjacent to but axially spaced from the projecting portion of the first leg.

[111 3,764,942 [451' 1 Oct. 9, 1973 ARRANGEMENT FOR WIDE BAND FOREIGNPATENTS OR APPLICATIONS COUPLING OF A COAXIAL LINE TO A HOLLOW CONDUCTOR52,864 6/1944 France...............;.........

[75] Inventors: Siegfried Keim; Eckart Schmid, Primary Examiner-Paul L.Gensler Attorney-Benjamin H. Sherman et al.

both of Muenchen, Germany ABSTRACT An arrangement for wide bandinductive coupling of a coaxial line to a hollow conductor, by means ofa coupling loop having a first leg extending in axial direc- [22] Filed:

[21] Appl. No.: 280,841

t1on from the inner conductor of the coaxial line mto the hollowconductor, and a second leg extending Foreign Application Priority Datatransversely from the first leg to the wall of the hollow conductor,with the free end portion of such first leg projecting beyond the secondleg into the hollow con- Germany................... P 21 42 863.7

Aug. 26, 1971 333/33, 333/97 R, 333/98 R ductor, at least two adjustablepins being provided for [51] Int. Cl. II0lp 5/08 determining thecoupling characteristics which pins extend inwardly from the hollowconductor sidewall,

one of such pins being disposed opposite the first leg and extendinginwardly toward the latter, while a second of such pins is disposedadjacent to but axially spaced from the projecting portion of the firstleg.

R aw 3 R RN. S 13 T 23 N 3 E 3 T 3 d H mm s SE mm m T a has h 6D c n E &w N m U 0 M F N M 5 U 3,101,459 v 8/1963Overholser............................ 333/33 10 Claims, 3 DrawingFigures VIIAQ rill/10r mm W l BACKGROUNDOF THE INVENTION The inventionis directed to an arrangement for effecting a wide band inductivecoupling of acoaxialline to a hollow conductor employing a coupling lookextending from the inner conductor of the coaxial line into the'hollowconductor, in axial direction, and ultimately terminated at the sidewallof the hollow conductor.

Arrangements of this general type are already known. For example, seethe publication Micro- Transmissions Circuits, Ragan, 1948, pages 354and 355. As brought out in publications such as that re- ?ferred to itis usually stated that such inductive coupling arrangementshave a numberof disadvantagesas compared to arrangements employing capacitivecoupling, in view of which prior arrangementsnormally employ capacitivecoupling. One of the principal disadvantages in such prior inductivecoupling arrangements ,was the fact that they were efficient over only avery small band and thus werenot suitable for most applications.

With the. various types of frequency modulation tubes, the problem ofeffecting a transition from a cou- "pling or decoupling hollowconductor, cooperable with the tube, to a coaxial line frequently arisesas in most instances the users of suchtubes prefer to use coaxial linesin their particular arrangements. As there is a continual and increasingdemand for size reduction in connection with such tubes and circuits, itis extremely difficult in many cases, and at times even impossible, toprovide a capacitive coupling of the coaxial line to the hollowconductor, since the coaxial line, for this purpose, must be connectedto the side of the hollow conductor. This in turn, creates structuraldifficulties, particularly keeping in mind the fact that such frequencymodulation tubes always require a magnetic system for the guidance ofthe electron beam.

The invention therefore is directed to the problem of producing anarrangement for wide band inductive coupling of a coaxial line to ahollow conductor, in which the coaxial line does not have to beconnected to the hollow conductor at the side thereof.

SUMMARY OF THE INVENTION The present invention employs an arrangement inwhich the coaxial cable extends in the same direction as the hollowconductor and employs a coupling loop which extends from the innerconductor of the coaxial line into the hollow conductor. The couplingloop is provided with a first leg extending, in the axial direction ofthe inner conductor of the coaxial line, into the hollow conductor, anda second leg extending from the first leg to the hollow conductor wall,with the first leg extending beyond the connection thereof to thesecondleg. In accordance with the present invention, cooperable with suchcoupling loop are at least two adjustable pins (which may be termedtrimming pins), which are mounted on the hollow conductor and extendlaterally into the latter, with a first pin being located in opposedrelation to the first leg of the coupling loop and a second pin disposedadjacent the free end of the projecting portion of the first leg. Veryfavorable conditions arise if the second pin extends inwardly from thehollow conductor wall to which the second leg of the coupling 2 loop isconnected, whereby suchpins-extend inwardly from opposite walls of thehollow conductor.

In order to achieve a smooth transitionfrom the:hollow conductor to thecoaxialline thecoupling loop, at

least a portion of the'loop-associatedwith the first 'leg is constructedas a strip line, whereby it thus becomes possible to match theimpedanceof the strip line to that of the coaxial line. I

As in many cases in which transitions of the type hereinvolved are ofspecial importance, namely for the transitional coupling ofhollowconductors of a frequency modulation tube to'external coaxialconnection lines, flat hollow conductors are usually'employed, and

in view of their relatively small height or thickness (theirlesserdimensionyit is desirable, for achieving a sufficient effective lengthof the coupling loop, to attach the latter eccentrically at theadjacentend of the inner conductor of the coaxial line. It-isparticularlydesirable to further reduce the actual length of the firstleg, to prevent undesirable extension of the coupling loop into thehollow conductor, which may disturb the transition from the tube to thehollow conductor, and at the same retain an effective length sufficientto achieve a adequately large effective coupling loop, the space betweenthe coupling loop and the wall of the hollow conductor contacted therebyis filled, at least partially, by a dielectric. The hollow conductorwavelength is thereby decreased in this area whereby a smaller axialgeometric length of the coupling loop corresponds to a sufficientlylarge effective electrical length.

In a particularly advantageous and stable structure, in accordance to afurther feature of the invention, the second leg of the coupling loop isof tubular construction and suitably connected, for example by solderingto one side of the first leg, with such tubular second leg being securedto the hollow conductor sidewall by a screw extending through anopening-in-the wall-and threaded into the second leg. I

The cooperable adjustabletrimming pins may be of very simpleconstruction i.e., in theform of screws which are threaded intocooperable bores in the hollow conductor sidewall, and if the couplingarrangement is to be employed in an evacuated area may be secured invacuum tight relationship to the conductor sidewall, followingcompletion of the desired optimum; adjustment, for example by solderingor the like.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings where like referencecharacters indicate like orcorresponding parts:

FIG. 1 is a longitudinal section through a coupling arrangementaccording to the invention;

FIG. 2 is a plan view of merely the coupling loop and inner conductorofthe coaxial line; and

FIG. 3 is a side elevational view thereof, with the coupling loop beingillustrated in section.

DETAILED DESCRIPTION A PREFERRED EMBODIMENT OF THE INVENTION Referringto FIG. 1 the reference numeral I generally designates a flat hollowconductor, adapted to be connected atthe ring 15 to a frequencymodulation tube (not illustrated), while the reference numeral 2generally designates a coaxial line section comprising an outerconductor 3 and an inner conductor 4 which are concentrically disposed,with the inner conductor being rigidly connected to the outer conductorby a dielectric sleeve or plug 6, whereby the coaxial line section andthe flat hollow conductor extend in the same longitudinal direction. Theouter conductor 3 of the coaxial line section may be provided with aflange 5 or other suitable construction by means of which the coaxialline section may be operatively connected to a cooperable coaxial line.

Extending into the adjacent end of the hollow conductor is a couplingloop having a first leg 9, extending in the same direction as the axesof the coaxial section 2 and hollow conductor 1, and a second legextending transversely to the first leg and contacting the adjacent wall7 of the hollow conductor.

The first leg of the coupling loop is designed as a strip line,providing an inductive coupling of the coaxial line 2 to the hollowconductor 1, and as illustrated in FIGS. .1 and 3 is connected, by meansof solder or the like, in eccentric relation to the adjacent inner endof the inner conductor 4, while the second leg 10 is of tubularconfiguration having an internally threaded bore in which ,a mountingscrew 12, extending through the side wall of 7 of the hollow conductor,is threaded to firmly ,mount the second leg 10 rigidly to the adjacentside- ,wall. It will be appreciated, however, that instead of thepreferred tubular construction, the second leg could be constructed inthe form of a small strip or wire which .is soldered to the inner faceof the hollow conductor wall 7. The first leg 9 of the coupling loop, asillustrated in FIGS. 1 and 3, is extended, for adjustment purposes,longitudinally beyond its connection to the second leg 10, with the freeend of the leg 9 forming an extension section or projection 11.

In order to effect a decrease in the hollow conductor wave length in theregion adjacent the coupling loop, and to achieve a sufficiently largeelectrical length of the coupling loop while employing a relativelyshort first leg 9, the space defined by the legs 9 and 10, and theadjacent hollow conductor wall 7 may be at least partially filled with adielectric material, for example a small ceramic block 16.

The physical length of the leg 9 thus can be relatively small withoutimpairing the coupling, whereby the entire coupling arrangement isdisposed relatively remote from the ring 15, which if disposed too closeto the ring might have a disturbing effect with respect to thetransition from the tube to the hollow conductor. Extending inwardlytransversely with respect to the axis of the hollow conductor, are aplurality of adjustable trimming pins, two such pins 13 and 14 beingemployed in the illustrated embodiment of the invention, which may be ofvery simple construction, for example in the form of screws threadedinto the hollow conductor sidewall.

The first such pin 13 is mounted in the wall 8 of the hollow conductorwith the free inner end of the pin 13 being disposed in opposition tothe first leg 9 of the coupling loop, while the second pin 14 is mountedin the opposing wall 7 of the hollow conductor and is positionedinwardly along the hollow conductor axis with respect to the projectingend 11 of the first leg 9 of the coupling loop, as will be apparent froma reference to FIG. 1.

The optimum adjustment, determinative of the magnitude of the coupling,and width of the coupling band, is dependent upon the adjustment of thedistance each pin extends into the hollow conductor, which adjustmentmay be readily effected by suitable rotation of the respective screwsforming the pins.

It will be apparent that the physical and electrical parameters of thecoupling arrangement illustrated may be readily determined by thoseskilled in the art to meet particular operating conditions.

Likewise if, the coupling arrangement is associated with an evacuatedconductor, the connection between the second leg 10 and the side wall 7,including the screw 12, as well as the junctures between the screws 13and 14 and their respective sidewalls, may be rendered vacuum-tight bysoldering or the like, such so]- dering of the screws 13 and 14 takingplace following the optimum adjustment thereof.

' Having thus described our invention, it will be obvious that althoughminor modifications might be suggested by those versed in the art, itshould be understood that we wish to embody within the scope of thepatent warranted hereon all such modifications as reasonably andproperly come within the scope of our contribution to the art.

We claim:

1. An arrangement for wide band inductive coupling of a coaxial line toa hollow conductor, comprising a coupling loop having a first legextending in axial direction from the inner conductor of the coaxialline into the hollow conductor, and a second leg extending transverselyfrom the first leg to the wall of the hollow.

conductor, with the end portion of said first leg projecting beyond thesecond leg into the hollow conductor, and at least two adjustabletrimming pins extending inwardly from the hollow conductor sidewall, oneof such pins being disposed opposite said first leg and extendinginwardly toward the latter, and a second of such pins being disposedadjacent to but axially spaced from the projecting end portion of saidfirst leg.

2. An arrangement according to claim. 1, wherein the second adjustablepin extends inwardly from the hollow conductor wall to which the secondleg of the coupling loop is connected.

3. An arrangement according to claim 1, wherein the space defined by therespective legs of the coupling loop and adjacent hollow conductor wallis at least partially filled by a dielectric.

4. An arrangement according to claim 1, wherein at least the first legof the coupling loop is in the form of a strip line.

5. An arrangement according to claim 1, wherein the coupling loopextends eccentrically with respect to the inner conductor of the coaxialline.

6. An arrangement according to claim 1, wherein the second leg of thecoupling loop is of tubular configuration and secured to the hollowconductor wall by a screw extending therethrough and threaded into saidsecond leg.

7. An arrangement according to claim 1, wherein said adjustable pins arein the form respective screws extending from the exterior into threadedbores in the hollow conductor walls.

8. An arrangement according to claim 7, wherein said screws aresoldered, in their adjusted positions, to the hollow conductor.

9. An arrangement according to claim 1, wherein said first leg of thecoupling loop extends eccentrically with respect to the inner conductorof the coaxial line and at least such first leg is in the form of astrip line, said second leg being of tubular configuration and securedto the hollow conductor wall by a screw extending therethrough andthreaded into said second leg, the

space defined by the respective legs of the coupling loop and adjacenthollow conductor wall being at least partially filled by a dielectric,said second adjusting'pin extending inwardly from the hollow conductorwall to which the second leg of the coupling loop is connected,

sitions, to the hollow conductor.

1. An arrangement for wide band inductive coupling of a coaxial line toa hollow conductor, comprising a coupling loop having a first legextending in axial direction from the inner conductor of the coaxialline into the hollow conductor, and a second leg extending transverselyfrom the first leg to the wall of the hollow conductor, with the endportion of said first leg projecting beyond the second leg into thehollow conductor, and at least two adjustable trimming pins extendinginwardly from the hollow conductor sidewall, one of such pins beingdisposed opposite said first leg and extending inwardly toward thelatter, and a second of such pins being disposed adjacent to but axiallyspaced from the projecting end portion of said first leg.
 2. Anarrangement according to claim 1, wherein the second adjustable pinextends inwardly from the hollow conductor wall to which the second legof the coupling loop is connected.
 3. An arrangement according to claim1, wherein the space defined by the respective legs of the coupling loopand adjacent hollow conductor wall is at least partially filled by adielectric.
 4. An arrangement according to claim 1, wherein at least thefirst leg of the coupling loop is in the form of a strip line.
 5. Anarrangement according to claim 1, wherein the coupling loop extendseccentrically with respect to the inner conductor of the coaxial line.6. An arrangement according to claim 1, wherein the second leg of thecoupling loop is of tubular configuration and secured to the hollowconductor wall by a screw extending therethrough and threaded into saidsecond leg.
 7. An arrangement according to claim 1, wherein saidadjustable pins are in the form respective screws extending from theexterior into threaded bores in the hollow conductor walls.
 8. Anarrangement according to claim 7, wherein said screws are soldered, intheir adjusted positions, to the hollow conductor.
 9. An arrangementaccording to claim 1, wherein said first leg of the coupling loopextends eccentrically with respect to the inner conductor of the coaxialline and at least such first leg is in the form of a strip line, saidsecond leg being of tubular configuration and secured to the hollowconductor wall by a screw extending therethrough and threaded into saidsecond leg, the space defined by the respective legs of the couplingloop and adjacent hollow conductor wall being at least partially filledby a dielectric, said second adjusting pin extending inwardly from thehollow conductor wall to which the second leg of the coupling loop isconnected, said pins comprising respective screws extending from theexterior through threaded bores in the hollow conductor walls.
 10. Anarrangement according to claim 9, wherein said adjusting screws aresoldered, in their adjusted positions, to the hollow conductor.